title: The Src family kinase inhibitors PP2 and PP1 block TGF-beta1-mediated cellular responses by direct and differential inhibition of type I and type II TGF-beta receptors.
abstract: Both the nonreceptor tyrosine kinase Src and the receptors for transforming growth factor (TGF)-β (TβRI, TβRII) play major roles during tumorigenesis by regulating cell growth, migration/invasion and metastasis. The common Src family kinase inhibitors PP2 and PP1 effectively block Src activity in vitro and in vivo, however, they may exert non-specific effects on other kinases. In this study, we have evaluated PP2 and PP1 for their ability to inhibit TGFβ1-mediated responses in the TGF-β-responsive pancreatic adenocarcinoma cell line Panc1. We show that PP2 and PP1 but not the more specific Src inhibitor SU6656 effectively relieved TGF-b1-induced growth arrest and p21(WAF1) induction, while basal growth was enhanced by PP2 and PP1, and suppressed by SU6656. PP2 and PP1 but not SU6656 also suppressed TGF-β1-induced epithelial-to-mesenchymal transition (EMT) as evidenced by their ability to inhibit downregulation of the epithelial marker E-cadherin, and upregulation of the EMT-associated transcription factor Slug. Likewise, PP2 and PP1 but not SU6656 effectively blocked TGF-β1-induced activation of Smad2 and p38 MAPK and partially suppressed Smad activation and transcriptional activity on TGF-β/Smad-responsive reporters of a kinase-active TβRI mutant ectopically expressed in Panc1 cells. Interestingly, PP2 and PP1 strongly inhibited recombinant TβRI in an in vitro kinase assay, with PP1 being more potent and PP2 being nearly as potent as the established TβRI inhibitor SB431542. PP2 but not PP1 also weakly inhibited the TβRII kinase. Together, these data provide evidence that PP2 and PP1 are powerful inhibitors of TβR function that can block TGF-β/Smad signaling in a Src-unrelated fashion. Both agents may be useful as dual TGF-β/Src inhibitors in experimental therapeutics of late stage metastatic disease.
authors.affiliation: Clinic for Applied Cellular Medicine at the UKSH, Campus Kiel, 24105 Kiel, Germany. hendrik.ungefroren@uk-sh.de
authors.forename: Hendrik
authors.initials: H
authors.lastname: Ungefroren
authors.forename: Susanne
authors.initials: S
authors.lastname: Sebens
authors.forename: Stephanie
authors.initials: S
authors.lastname: Groth
authors.forename: Frank
authors.initials: F
authors.lastname: Gieseler
authors.forename: Fred
authors.initials: F
authors.lastname: Fändrich
mesh_terms: D001549:Benzamides / Q000494:pharmacology; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D048708:Cell Growth Processes / Q000187:drug effects; D002460:Cell Line; D045744:Cell Line, Tumor; D004149:Dioxoles / Q000494:pharmacology; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011720:Pyrazoles / Q000494:pharmacology*; D011743:Pyrimidines / Q000494:pharmacology*; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051899:Smad2 Protein / Q000378:metabolism; D000071250:Snail Family Transcription Factors; D013449:Sulfonamides / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D019061:src-Family Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism*
chemical_list: C459179:4-(5-benzo(1,3)dioxol-5-yl-4-pyridin-2-yl-1H-imidazol-2-yl)benzamide; C108123:4-amino-5-(4-methylphenyl)-7-(tert-butyl)pyrazolo(3,4-d)pyrimidine; C412373:AG 1879; D001549:Benzamides; D015820:Cadherins; D004149:Dioxoles; D007211:Indoles; D011720:Pyrazoles; D011743:Pyrimidines; D018125:Receptors, Transforming Growth Factor beta; C497782:SMAD2 protein, human; C000604407:SNAI1 protein, human; C416927:SU 6656; D051899:Smad2 Protein; D000071250:Snail Family Transcription Factors; D013449:Sulfonamides; D014157:Transcription Factors; D053773:Transforming Growth Factor beta1; D019061:src-Family Kinases; D017346:Protein Serine-Threonine Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II